1. Field of the Invention
The present invention relates to a steel stock cooling apparatus for water cooling in heat treatment of steel stocks.
2. Description of the Prior Art
Recently, there has been seen a strong tendency that it is planned to produce steel plates of high quality and decreased cost by heat treatment, particularly by water-cooling, and a great development has been marked in the so-called controlled cooling technique in which cooling is effected reliably in conformity with a desired cooling curve.
There have been generally adopted, as the cooling method of the type described above, a continuous cooling method in which, to uniformly and efficiently cool a steel plate, water or water mixed with air is injected from a nozzle onto the traveling steel plate. The cooling method is chosen from among a jet spray, a mist spray and a fog spray depending upon the type of the various desired cooling capacities.
In order to further efficiently effect cooling, it is necessary to form the above three types of injections consisting of water or water mixed with air by use of one type of nozzle in accordance with the desired cooling capacity. Namely, it becomes necessary to provide a cooling apparatus in which a stabilized cooling pattern is maintained and the cooling capacity is controlled over a wide range by use of a single nozzle.
Along with the progress of the continuous cooling method of the type described above, there has been widely seen the development in the controlled cooling technique in which, to efficiently manufacture steel stocks of high quality, cooling is effected in conformity with a predetermined cooling curve. There has been proposed an injecting apparatus using two fluids including water and air and capable of controlling the cooling capacity over a wide range by use of a single nozzle.
However, it is known that the injecting apparatus described above requires complicated manufacturing work, the cooling pattern thereof is limited to a circle, and is suitable for cooling a small area but inefficient in cooling a large area. Additionally, the conventional means has been still utilized in the technique of varying the cooling capacity by changing the flow rate, pressure and the like of water and air from the injection nozzle. The conventional control means as described above has been of the type in which the cooling capacity is controlled by changing the injected water stream and velocity of the mixed two fluids from the injection nozzle by separately controlling either one or both of the water flow rate (pressure) supplied and the air pressure (flow rate) supplied to the injection nozzle. Accordingly, with the conventional control means, there have been such disadvantages that, in the case that either the water amount supplied or the air pressure supplied is controlled, either one of the former or the latter is supplied beyond the need to result in not only the waste of power but the failure in obtaining the cooling capacity over a wide range, and in the case that both the water amount and the air pressure are separately supplied, the control is difficult to be conducted, because the varying of either one of the former or the latter is followed by the fluctuation of the other, whereby troublesome valve operation is necessitated to obtain a required cooling capacity, thereby making the conventional control means unfitted for the controlled cooling apparatus for steel stocks, which requires a speedy and accurate control.